The present invention relates to a metal mould for use in a moulding process, and particularly to a porous metal mould obtained by sintering metal powder, and a method for producing such a metal mould. Further, this invention relates to a sintered metal mould or a sintered porous metal mould for use in a moulding process and which is moulded from metal powder by a pressure forming method, and to a method for producing the same.
Heretofore, in producing a production type metal mould for use in a vacuum forming process, pressure forming process, blow forming process, injection forming process and the like, a mould for trial production is first formed and, thereafter, moulds for mass production are formed based on the trial production mould. The following two procedures are used in forming the mould for trial manufacture.
The first method is as follows: the manufacturer of the metal mould makes a master model having the shape of the final product, said master model being based on the drawings supplied from the client and made from timber, plaster, synthetic resin or easily machineable metal and the like. Next, by utilizing a pouring type epoxy resin containing metal powder, a mould for trial production having a reversed form to the master model is formed.
According to the second method, the manufacturer of the metal mould, based on the drawings supplied from the client, makes directly the mould for trial manufacture, by machining a material such as easily machineable aluminum or bronze.
The first method is, compared with the second method, advantageous in that the method is simple and that the time for producing the mould for trial manufacture is short. However, the mould of the first method is inferior to the mould of the second method in respect of pressure resistivity, thermal resistivity, abrasion resistivity and thermal conductivity. Thus, the first method cannot be applied to the mould of a material such as polycarbonate resin or a compound material including glass fiber in which the injection should be performed at high pressure and high temperature. Further, the heat conductivity of the mould itself is very poor, thus, a long time is required to cool the mould sufficiently. As a result, the characteristics of the article formed by utilizing the mould of the first method is inferior to the article formed by utilizing the mould of the second method which utilizes a metallic material having excellent thermal conductivity.
Accordingly, the maker of the mould first utilizes the epoxy resin and the like in making the mould of the trial production and produces a trial product utilizing a material which permits injection moulding at a lower pressure and temperature than that of the final product, which material is different from that of the final product namely a compound material of polycarbonate resin. The maker then sends the trial product to the purchaser to confirm the configuration and the function of the trial product and, if required, corrects the mould of the trial production and re-confirms. Thereafter, the drawings for the final mould are determined.
When the drawings of the final mould are determined, a mould for use in production is prepared. Usually, such a mould is formed of a well known metal for use in a metallic mould by processing means such as an electric discharge machining technique and the like.